Simulations And Analysis Of Land Use Change And Climate Change Impacts On Catchment Runoff Based On HSPF

Land use and land cover change(LUCC)and climate change are important factors affecting runoff change.Under the influence of human activities,the spatial structure of land use changes,resulting in changes of water cycle,such as surface evapotranspiration,interception of surface vegetation,infiltration capacity of soil water,surface water and groundwater,and thus directly or indirectly affecting the runoff process of the basin.Climate change directly affects water cycle processes such as precipitation and temperature,and then affects a series of hydrological processes such as surface evapotranspiration,soil water infiltration capacity and runoff,and finally leads to changes in regional runoff.Jinjiang Watershed is located in Quanzhou city,southeast coastal area of China.It is one of the regions with the most rapid economic development and the most dynamic in Fujian Province.Frequent human activities lead to great changes in land use,and the total amount of water resources in the basin is rich,which is prone to flood disasters in summer.The change of runoff directly affects the safety of people’s life and the sustainable development of social economy.Therefore,taking this basin as the study area,it is highly representative to discuss the runoff response of different time scales under the future LUCC and climate change,which can also provide an important theoretical basis for the formulation of disaster prevention and mitigation policies and watershed water resources management programs in this region.Based on FLUS(Future Land Use Simulation)model,the Land Use change in Jinjiang Basin in 2030 under both natural and conservation scenarios was predicted.The LUCC was analyzed at the spatial scale of the whole basin and its sub-basins.Climate data from 2030 to 2049 in three GCMs models(BCC-CSM2-MR,MIROC6,MRI-ESM2-0)under CMIP6 were selected,and the QM downscaling method was adopted.To achieve the downscaling of temperature and precipitation under three shared socio-economic paths(SSP126,SSP245 and SSP585),and to analyze the change rules of precipitation and temperature in the future.On this basis,a daily scale Hydrology Simulation Program Fortran(HSPF)hydrological model was constructed to explore the runoff response of the basin under the influence of LUCC and climate change on the time scales of year,month and day.The main conclusions are as follows:(1)From 2010 to 2030,the LUCC of Jinjiang Watershed mainly showed that the area of construction land and garden land increased,while the area of forest land and cultivated land decreased.Under the natural scenario,the area of construction land and garden land increased by 61.0% and 23.6% respectively,while the area of forest land and cultivated land decreased by 9.0% and 17.7% respectively.Under the protection scenario,the degree of LUCC in The Jinjiang Watershed was smaller than that in the natural scenario.The area of construction land and garden land increased by 55.0% and 17.7%,while the area of forest land and cultivated land decreased by 7.0% and 17.3%,respectively.Spatially,the LUCC of Anxi sub-basin and Shanmei Reservoir Sub-basin is consistent with that of the whole basin under the two scenarios,and the LUCC of Anxi Sub-basin is more significant.(2)Compared with the baseline period,the annual precipitation in Jinjiang Watershed under SSP126,SS245 and SSP585 scenarios will increase by 4.6%,3.1% and2.4%,and the annual temperature will increase by 0.1℃,0.1℃ and 0.5℃,respectively,from 2030 to 2049.On the monthly time scale,under SSP126,SSP245 and SSP585,the monthly precipitation decreased from March to May,August and October,and increased in other months.The monthly mean temperature basically showed that the monthly mean temperature from March to June,August and December increased,and the temperature in other months decreased.In addition,there are significant differences in precipitation and temperature between different GCM models.(3)LUCC will lead to a small increase in annual runoff in the future,and the increase of annual runoff in the three hydrological stations under natural scenarios is0.83%-2.45%.Under the conservation scenario,the annual runoff increase was0.78%-2.20%.The increase range of annual runoff is as follows: Jinjiang Basin >Shanmei Reservoir basin > Anxi Basin.The annual mean monthly runoff increased from January to September,but decreased in other months.The increase of runoff was the most obvious in March,with the increase of 4.96%,2.57% and 4.40% at each site under the natural scenario and 4.42%,2.23% and 3.77% under the conservation scenario,respectively.In terms of daily runoff,Q10 increased and Q90 decreased in the three hydrological stations,and the response of runoff from stone hulling station was the most obvious.(4)Under the future climate scenario,the annual runoff of the three hydrological stations shows an overall increase trend,and the increase is SSP126>SSP245>SSP585.The annual average monthly runoff showed an increasing trend from November to April,June to July and September of the next year,and decreased in other months.In SSP585 scenario,the monthly runoff fluctuated the most,with an increase range of-2.25% to13.64%.The annual average Q10 of the three hydrological stations increased by 16.31%,11.28% and 4.26% in SSP126,respectively.The multi-year average Q90 increased most significantly in SSP126,which increased 10.97%,14.36% and 10.70%,respectively.(5)The annual runoff increased the most(9.10%～15.15%)under the mixed scenario of SSP126 and natural land use change,and the least(4.77%～10.81%)under the mixed scenario of SSP585 and conservation land use change.The trend of annual average monthly runoff at each hydrological station is similar to that under single climate change.For daily runoff,except for Shanmei Reservoir station,the increase of Q10 and Q90 was more than 5%,and the increase of Shilong Station was the most obvious,with the increase range of Q10 being 10.79%-17.36%,and that of Q90 being 8.95%～12.09%.Compared with single climate change or LUCC scenarios,the runoff response under the synergistic effects of climate change and LUCC is more significant.The impact of future climate change on runoff is significantly greater than that of LUCC.